CN87104449A

CN87104449A - Metering device

Info

Publication number: CN87104449A
Application number: CN198787104449A
Authority: CN
Inventors: 戴维·纳特勒顿; 亚延蒂拉尔·A·帕特尔; 阿兰·杰拉尔德·梅里尔斯
Original assignee: Rank Taylor Hobson Ltd
Current assignee: Rank Taylor Hobson Ltd
Priority date: 1986-06-27
Filing date: 1987-06-27
Publication date: 1988-02-03
Also published as: JPS6336107A; IN169910B; EP0254429A1; EP0254429B1; GB2192062A; US4825557A; DE3781342D1; GB8615772D0; GB2192062B; RU1769805C; JP2528659B2; DE3781342T2

Abstract

A metering instrument includes an inductive sensor with a stylus all housed in a protective housing. At the beginning of the measurement operation, the sensor is driven so that the stylus moves along a circular path: the stylus first emerges from the housing at high speed, then moves to contact the workpiece surface, and then moves across the workpiece surface at a relatively low speed for measurement. After completion, the stylus is retracted into the housing at high speed. These movements are all accomplished by a single motor driving a series of cams. Such an instrument can be installed next to the production line without risk of damage to the instrument, and it can be used to inspect a large number of identical parts produced in each batch production process.

Description

Metering device

The present invention relates to metrology and, more particularly, to instruments that measure characteristics of a workpiece, such as surface radius, shape, and surface texture.

When machining precision parts, it is necessary to inspect the surfaces to ensure that they meet the specifications of the end user, these inspections being carried out by means of precision and highly sensitive metrology instruments, which are conventionally placed in dedicated measurement chambers remote from the production line in order to prevent accidental damage, and therefore it is necessary to transfer the parts from the production line to the measurement chambers for inspection and then back to the production line for further processing. This is time consuming and therefore expensive, and there is a need to improve the efficiency of the measuring operation, particularly where a large number of identical parts are produced and it is desired to inspect each. Traditionally, the development of metrology instruments has focused on increasing the accuracy of the instrument by improving the measurement procedure, and increasing the speed of operation and the procedure being computer controlled in modern instruments. Such an effort to increase the speed obviously only results in a reduction of the time of the measurement operation itself.

It is an object of the present invention to greatly improve the efficiency of inspection of a large number of identical parts.

In one aspect, the present invention provides a metrology apparatus in which a detector for inspecting the surface of a workpiece is provided and is movable between a retracted position when within a protective housing and an operative position when extended outside the protective housing for contact with the surface of the workpiece to be inspected.

In another aspect, the invention provides a metrology apparatus with a drive arrangement that can move a detector repeatedly along or around a predetermined path to measure a series of identical workpieces. In the preferred embodiment, means are provided for setting the apparatus to one of a plurality of conditions, each condition providing a different one of said predetermined paths, so as to enable the instrument employed to inspect a variety of different parts.

Another aspect of the invention is to provide an apparatus which can be actuated by pressing an actuation key to complete a predetermined measurement cycle to repeat the cycle for a series of similar workpieces.

In a further aspect, the invention provides an apparatus comprising first means for inputting preparatory instructions and/or data and second means, separate from the first means, for repeatedly starting a predetermined measurement cycle. The second means is preferably a key. The first device is preferably a terminal separable from the instrument.

In another aspect, the invention provides a method of producing a plurality of identical workpieces, wherein at least a majority of said products are subjected to a metrology operation.

The invention will now be further described, by way of example, with reference to the accompanying drawings. In the drawings:

FIG. 1 is a perspective view of an apparatus in accordance with a preferred embodiment of the present invention;

FIG. 2 is an explanatory diagram showing the operation principle of the preferred embodiment of the present invention;

FIG. 3 is a partial cross-sectional view of the preferred embodiment of the present invention;

FIG. 4 is a cross-sectional view similar to FIG. 3 but showing the instrument in another state;

FIG. 5 is an enlarged view of the cam track in the instrument of FIGS. 3 and 4;

FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 3;

FIG. 7 is a plan view of the instrument of FIG. 3;

FIG. 8 is an explanatory diagram showing the operation of a portion of the apparatus of FIG. 7;

FIG. 9 is a partial cross-sectional view taken along line IX-IX of FIG. 6;

FIG. 10 is a partial cross-sectional view of the portion of the instrument shown in FIG. 9, but from an opposite direction;

FIG. 11 is a plan view of a movable clamp for setting up the instrument;

FIG. 12 is a side view, partially in section, of the clamp of FIG. 11, shown mounted on an instrument;

FIG. 13 is a plan view of another fixture for the aligner;

FIG. 14 is a side view, partially in section, of the clamp of FIG. 13 when on an instrument;

FIG. 15 is a block diagram of the circuitry of the preferred embodiment of the present invention;

FIG. 16 illustrates a display produced on a display device included in a preferred embodiment of the present invention;

FIG. 17 illustrates another display that may be produced;

FIG. 18 is an explanatory diagram useful in understanding the calibration operation performed by the instrument of the previous figures;

FIG. 19 is an explanatory diagram to help understand the measurement operation of the preferred embodiment;

FIG. 20 is a perspective view of another form of clip that may be used in the preferred embodiment.

Referring to fig. 1, the apparatus includes a host computer 500, a terminal 502 and a printer 504,

the mainframe 500 includes a housing 506, a workpiece support structure 508 mounted on the top 6 of the housing 506, and a measurement tool 510, the structure 508 and the tool 510 being described in more detail in connection with other figures. The tool 510 is located in a chamber 512 defined between a front wall 514 of the housing 506, a pair of side baffles 516 and a transverse baffle 518. a fan 520 located in the chamber 512 draws ambient air from the lower portion of the housing 506 through apertures in a floor 522 thereof into the chamber 512, which air passes through the tool 510 and is exhausted from the upper edges of the baffles 516, which are spaced below the top 6 of the housing 506. Electrical and electronic circuitry (not shown in fig. 1) is located in compartment 524 near the rear of housing 506. Air flows through the compartment 512 due to the action of the fan 520, maintaining the tools 510 at ambient temperature and preventing them from being heated by air from the compartment 524. This arrangement is particularly advantageous for stabilising the accuracy of the instrument, since it has been found that the air flow rapidly brings the instrument to a steady state. In this regard, temperature changes of the tool 510 may cause it to thermally expand or contract, again compromising the accuracy of the measurement.

Forward facing

digital displays

526 and 528 are mounted near the rear of the housing 506. An information display panel 530 is positioned in front of the display 526 to indicate the meaning of a certain numeric code appearing on the display 526.

Switches

532, 534, and 536 are provided to turn the power on and off, respectively, to start the printer 504, to print the measurement result, and to start the measurement operation.

Terminal 502 includes a keypad 538 and a liquid crystal display 540 capable of displaying curves and tables. Terminal 502 and printer 504 are both connected to host 500 by a detachable cable 542.

In the following further detailed description of the structure and operation of the preferred embodiment of the present invention, it will be assumed that the instrument is used to measure the concave annular surface of a ball race.

Referring to fig. 2, the ball race 2 has a concave annular surface 4 whose radius and shape are to be inspected by the apparatus of the preferred embodiment of the present invention and which is one of many such races manufactured in a mass production process to be individually inspected. The meter performing this inspection is placed on a table (not shown) next to the production line under substantially no risk of damage and is used to perform the measuring cycle at high speed and high repetition rate, which is particularly suitable for the ball race 2 to be inspected.

The structure 508 includes a clamp (not shown in fig. 2) to support the seat ring 2 on the clamp. The stylus 8 (only the end of which is visible in fig. 2) can be moved once per measurement cycle around a closed path as indicated by the dash-dot line 10 in fig. 2. When the instrument is not operating, the stylus 8 is in position 12, in which it is retracted into the housing. At the same time, the hole 14 provided in the top part 6 is covered by the shield 16, so that the stylus is completely protected from accidental damage. When the instrument is in operation, the stylus is caused to move along path 10 in the direction indicated by arrow 15. Thus the stylus is first moved generally horizontally in a direction away from the workpiece from position 12 to position 18, and then it is moved vertically through the opening 14 to position 20. The shutter 16 has been removed in advance to expose the opening 14. The stylus is then moved generally horizontally towards the workpiece to a position 22 where it contacts the surface of the race 2. Thereafter, the stylus is moved further downward while keeping its end in contact with the surface to be inspected. In the downward movement, the output of a sensor associated with the stylus is sensed to enable the required measurement to be made. When the stylus is moved to point 24 it is moved horizontally to the right (as viewed in the figure) a small distance to disengage the end from the surface of the workpiece and back to position 12, completing a cycle. The movement of the stylus from points 22 to 24 is at a speed suitable for the measurement, typically slower. At other points, particularly between

points

18 and 20 and points 24 and 12, the movement is performed at a high speed, in order to reduce the time taken for the whole cycle. When the stylus returns to position 12, the flap 16 again moves over the opening 14.

If, during movement between

points

18 and 20, the stylus encounters an obstacle such as 26 or 26a, the instrument will detect this, and the stylus will first move horizontally to the right (as indicated by arrow 29), i.e. away from the workpiece, and then be retracted into the instrument housing and returned to position 12 along path 28 shown in broken lines, as indicated by arrow 30.

Referring to figures 3 to 6, the stylus 8 is mounted on an inductive sensor 32, the sensor 32 being mounted on the upper end of a vertically reciprocable rod 34, the rod 34 being slidable in bearings 36 located at the opposite end of a tubular housing 38. The housing 38 is fixed in a housing 40 which contains the sensor 32 and whose top 6 has been illustrated in fig. 2. The vertical reciprocation of the rod 34 and the transducer 32 is achieved by a lever 42, the central portion 44 of which lever 42 is pivotally connected to the housing 40 and has a fork 46 at one end which is inserted into a slot 48 in a transducer support structure 50. The other end carries a pin 52 inserted in a slot 54 of a cam 56, the cam 56 being fixed to a vertical shaft 58 driven by a constant speed motor 60. When the shaft 58 is rotated, the lever 42 swings from the position shown in figure 3 to the position of figure 4, moving the stylus from position 18 to position 20, and then swings back to the position of figure 3 to move the stylus from position 22 back to position 12. The shape of cam slot 54 is shown in fig. 5. When the pin 52 is in the cam 54a portion, the stylus is in position 12. When the cam 56 is rotated to move the pin 52 down to the steep portion 54b of the slot 54, the stylus 22 moves rapidly from position 18 to position 20. The portion 54c of slot 54 is slightly angled upward so that the sensor moves slowly from position 22 to position 24 at a constant speed as cam 56 rotates at a constant speed. Thus, during this constant movement, the stylus 22 passes over the surface being measured. At a predetermined point shortly after the start of this jump, a signal is generated by a light detecting element 61a (fig. 6) to initiate data recording, the element 61a being responsive to light passing through a slit (not shown) in the disc 63a, the disc 63a being fixed to the shaft 58 and rotating therewith. When the sensor 32 reaches position 24, the pin 52 enters a portion 54d of the sharp rise, causing the stylus 8 to move rapidly away from the position 24, returning to position 12 after being lifted off the surface of the workpiece. As shown in fig. 6, the light detecting member 61 detects a slit (not shown) formed in a disk 63 fixed to the shaft 58, and stops the motor 60 after the stylus is returned to the position 12, that is, after one rotation of the shaft 58.

The sensor 32 is mounted on the structure 50 by a parallel linkage which enables it to move generally horizontally, thereby enabling the stylus to move from position 12 to 18 and from position 20 to 22. The parallel linkage includes a generally vertically extending link 62, the upper end of the link 62 being pivotally connected to the sensor 32 and the lower end of the link 62 being pivotally connected to the structure 50. A vertically extending leaf spring 64 is fixed at its lower end to the structure 50 and at its upper end contacts the sensor 32 to urge the sensor 32 to the left in fig. 3 and 4. The spring force is adjustable by a screw 66 in such a way that the sensor 32 is held in its leftmost position as the stylus passes over the surface being measured. Movement of the sensor 32 to the right to move the stylus from position 12 to position 18 is achieved by the cam 70. A cam 70 is fixed to the shaft 58 and acts on the sensor 32 through a lever 72. A lever 72 is pivotally mounted at one end 72a to the housing 40 and has at its other end a roller 74 which engages the cam 70 and a low friction projection 76 which engages the sensor 32. Thus, when the motor 60 rotates the shaft 58 to begin moving the lever 34 upward, the cam 70 also rotates to move the sensor 32 to the right. It will be appreciated that although figure 2 shows the movement of the stylus from position 12 to position 18 horizontally, the movement also includes an upward component of movement using the mechanism illustrated in figures 3 to 5. When the stylus reaches position 20, the surface portion 70a of the cam 70 rotates to the position of the roller 74, thereby moving the sensor 32 to the left.

If during the upward movement from position 18 to position 20 the stylus 8 hits an obstacle, 26 as shown in fig. 2, the sensor 32 is displaced to the right. This is by means of a chamfered surface 8a provided at the upper end of the contact pin 8. A parallel linkage 62 is provided for this movement. On movement to the right, the plate 79 on which the sensor 32 is mounted moves into the light sensing element 81 which generates a signal to reverse the operation of the motor 60, so that the stylus is immediately retracted into its protective housing 40, thus minimising the risk of damage caused by such an obstruction.

As can be seen in fig. 3, 7 and 8, the flapper 16 is secured to one end of a shaft 80, the shaft 80 being surrounded by a torsion spring 82, the torsion spring 82 pressing the flapper 16 to a position that opens the aperture 14. The lower end of the shaft 80 is provided with a lever 84 having a roller 86 thereon, the roller 86 engaging a cam 88 secured to the shaft 58, a projection 88a of the cam 88 being positioned on the cam so that the shaft 58 engages the roller when the sensor 32 is fully lowered and the stylus 8 is correspondingly withdrawn into the housing 40. At the beginning of a measurement cycle, during rotation of the shaft 58, the portion 88a of the cam 88 moves away from the roller, causing the torsion spring 82 to move the flapper to the open position shown in phantom in FIGS. 7 and 8, in which the flapper engages a stop pin 90.

The movement of the stylus 8 out of contact with the workpiece surface at position 24 is achieved by means of a low friction follower 92 (see figure 6) mounted on the sensor 32, the follower 92 engaging a normally stationary cam 94 as can be seen in figures 6, 9 and 10. The cam 94 includes a step 94a arranged so that when the follower 92 bears against the step, the sensor 32 moves to the right so that the stylus 8 moves out of contact with the workpiece surface, the cooperation of the follower 92 and cam 94 causing the stylus 8 to move from position 24 to position 12 without contact with the workpiece surface. As can be seen from fig. 9 and 10, the vertical orientation of the position 24 can be adjusted by rotating the cam 94 about the horizontal axis of the cam 94. Once the position of the cam 94 has been selected based on the workpiece to be measured, the selected position can be maintained for all measurements of the same workpiece. However, if workpieces of different sizes are to be measured, the cam 94 can be rotated to a new position to adjust the vertical orientation of the position 24 so that the stylus is withdrawn from the surface of the workpiece after the desired portion of the surface of the workpiece has been measured. The rightward movement of the sensor is detected by a light detector 81a that detects a projecting portion 79a of the plate or vane 79.

The position of the cam 94 is selected to accommodate different workpieces and in accordance with the workpiece to be inspected. The instrument is equipped with a number of different clamps or fastening devices each designed for a specific workpiece. In fig. 7 and 10 to 11, a jig 100 is shown. Each clamp 100 has an aperture 102 and a slot 104, the aperture 102 and the slot 104 receiving a respective latch 106 secured to the top 6 of the housing 40 to secure the clamp in a desired position, and a rotatable securing means 108 (not shown or described in detail) for securing the clamp to the top 6. Each fixture has a positioning socket 110 of a size and shape to accurately position a workpiece of a predetermined size relative to an opening 112 in the fixture, the stylus being able to pass through the opening 112 when the stylus 8 is extended from the housing 40. A spring loaded lever 114 is provided for clamping the workpiece 2 in engagement with the seat 110. Each clamp has a downwardly extending pin 116 for determining the rotational position of the cam 94 based on the size of the workpiece supported by the clamp. The pin 116 is threadably (not shown) secured to the fixture 100 so that its position can be adjusted when installing the fixture for a particular size workpiece. As shown in fig. 10, pin 116 engages a plunger 118, plunger 118 being slidable in a sleeve 119 supported by head 6, the lower end of which engages a lever 120 fixed to a shaft 122, on which shaft 122 cam 94 is mounted. A spring biasing device (not shown) is used to bias the shaft 122 in a counterclockwise direction as viewed in fig. 10.

Figures 13 and 14 show a fixture 130 for calibrating an instrument which is identical to the fixture 100 except that it does not include the socket 110 nor the lever 114, but is equipped with a high precision ball 132, such as a high precision ball bearing, the high precision ball 132 being located in a precisely located recess 134 and held in place by means of a leaf spring 136, the leaf spring 136 being fixed to a block 138 on top of the fixture 130. The clamp 130 carries an element 140 which acts on a microswitch 142, the microswitch 142 being located on the underside of the top 6 of the housing 40 for fixing the instrument in a calibrated condition when the clamp is mounted on the instrument. Therefore, the calibration can be conveniently performed frequently as needed.

Referring to fig. 15, host 500 includes a microprocessor 600, and microprocessor 600 is equipped with associated memory 602, which is connected to terminal 502 and printer 504 via cable 542. The interface board 604 supplies control signals to the processor 600 in response to signals generated by the measurement and

print buttons

534 and 536, the calibration microswitch 142, and the

light sensing elements

81, 61a, 81a, 61 that respectively indicate an obstruction, start data recording, stop data recording, and stop the motor 60. Interface board 604 in turn supplies signals to

digital displays

526 and 528 under the control of microprocessor 600.

The dashboard 606 receives the analog output signal from the sensor 32 and converts this signal into digital form for supply to the microprocessor 600. The output of the sensor 32 is read at equally spaced positions of the sensor 32 as the sensor 32 moves across the workpiece surface, this being done by means of a position sensing device which senses the position of the sensor and which includes a grating device 608 and a plurality of optical heads 610, one of which is movable with the sensor and the other of which is fixed. Grating 608 is illuminated by light source 612.

Computer 600 is programmed so that when terminal 502 is connected the instrument is controlled by terminal 502 and any signals from the measure button or print button 534 are ignored. When the terminal 502 is disconnected and the instrument is controlled by the measurement button 536 and the print button 534, actuation of the measurement button 536 causes the processor 600 to perform a measurement cycle in which the sensor moves around the circular path shown in figure 2 and data from the sensor is recorded and measurements are taken on the data. This is an important aspect of the preferred embodiment of the present invention because with the terminal 502, a skilled operator can program an instrument, and after the instrument is programmed, a relatively unskilled operator can also measure a series of workpieces by simply placing the workpiece in the fixture and actuating the measurement button 536.

When the terminal 502 is connected to the processor 600, various programs can be entered by means of the item table displayed on the display 540, one of the most preferred main item table examples being as follows:

1. measurement/calibration

2. Results

3. Choreography

4. Inputting parameters

5. Printing profiles

6. Print summary

To program an instrument for a series of identical workpieces, it is necessary first to select the appropriate fixture 100 and second to adjust the position of the pin 116 to determine the orientation of the position 24. In one measurement cycle the stylus 8 is moved in position 24 out of contact with the workpiece surface. Thus, after the jig is selected, the jig is mounted on the instrument, and then a batch-produced one of the workpiece samples (ball race 2) to be measured is mounted in the jig. Item 3 is selected from the main item table, which results in a program to be entered wherein the coarse and fine scales 620, 622 are displayed on the liquid crystal display 540 with

variable indicators

624 and 626.

Variation indicators

624 and 626 are associated with coarse and fine scales 620 and 622, respectively, and provide images of the displacement of stylus 22 in millimeters, which is derived by processor 600 from the magnitude of the signal generated by the inductive sensor. The coarse scale 620 represents a deviation in the positive and negative directions from the zero point and includes a plurality of scales represented by 0.1 mm. The fine scale comprises a plurality of scales representing 0.01 mm offsets. A manual actuation button 628 (fig. 15) is used to turn the handler 600 on or off under the control of a skilled operator of the marshalling apparatus. The button 628 is preferably located on the instrument in a position where the button 628 is not readily accessible to a relatively unskilled operator who is to test the workpieces being produced in series. Using button 628 and observing the movement of

indicators

624 and 626, the operator of the programming instrument can move the sensor around the circular path shown in figure 2, by means of which the operator can observe the deflection of the stylus as it moves across the surface of the workpiece (including the concave portion) and as the sensor moves away from position 24. The position 24 is preferably located only a small distance below the lower end of the concave portion of the ball race 2, whereby adjustment of the position of the bulge 116 by means of the button 628 and the graduations 620 and 622 provides the desired orientation of the position 24 only a small distance below the concave portion of the ball race 2. In this way, the stop data recording signal generated by the element 81a is generated without any unnecessary delay, so that the processor 600 can start performing the required calculations on the data collected without any unnecessary delay, the calculations being performed in response to the signal from the element 81 a. The operating speed of the instrument can be increased.

Before using the device, it is also necessary to enter certain parameters, which is done by means of selecting item 4 from the main item table. As a response thereto, an input parameter table is displayed, one of the best examples of which is as follows:

1. unit (metric/English system)

2. Neglect percentage (0 … 30)

3. Radius of contact pin tip (5-99 microns)

4. Printing format (outline/summary)

With this table, the operator first enters the cell in which the measurement is to be made, and then he enters the so-called "ignore length". This can be understood from fig. 19, which shows the neglected lengths of the beginning and end of the measured concave profile. Therefore up to 30% of the curve length is ignored in the calculations performed. The specific selected data depends on the workpiece to be inspected. Figure 19 also shows the position 24 and shows the path of the stylus tip after it has left the surface of the workpiece in broken lines.

The radius of the tip of the stylus is then entered, along with the desired print format, i.e. whether the curved track is required only for digital printing of the radius and measurement of the peak to trough (P-V).

After the instrument has been programmed as described above, calibration must be performed prior to use. In fact, the calibration should be done regularly, e.g. once a day, even in the case of invariance after the device has been set up. To calibrate the instrument, a calibration fixture with calibration balls (FIG. 14) is mounted on the instrument. Calibration can be performed by selecting item 1 from the main item table (if the terminal is connected) or simply pressing the measure button 536. Figure 18 shows the portion of the sphere that is passed through during calibration, the path of the stylus tip after it leaves the surface of the sphere being shown in dashed lines. The device is pre-programmed with the radius and calibration sphere 132 form from which and from the data obtained in the calibration cycle the instrument performs the required calculations to complete the calibration. This can be done in a known manner and therefore need not be described further.

Item 2, selected from the list of primary items, allows the results previously stored in the instrument to be displayed, and items 5 and 6 provide instructions for printing a profile or print summary, independent of its selection from input parameters 4.

In the case of measurements taken while the terminal is connected, the results are displayed on the display 540 in the form shown in FIG. 17, where the horizontal straight line 630 represents the surface radius, the trajectory 632 represents the shape error, and the radius and P-V measurements are displayed on the upper portion of the display as shown. In addition, regardless of whether terminal 502 is connected or not, the radius is displayed by display 256 and the P-V is displayed by display 528.

From the foregoing, it can be appreciated that once the apparatus has been set up and calibrated, the apparatus can be used to inspect a series of identical workpieces with heretofore unattainable high efficiency. In particular, a relatively unskilled operator simply places each workpiece in the fixture and activates the measurement button to perform the test. Actuation of the measurement button causes the start of a measurement cycle which includes movement of the stylus around its circular path while initially rapidly extending, a change in speed to a speed suitable for data logging, movement of the workpiece for data logging purposes, lifting off the surface of the workpiece (which movement initiates the data calculation process in the computer), and rapid retraction to a parked position in the protective housing. Following the calculation of the recorded data, the computer displays the radius and the P-V value on two

digital displays

526 and 528, whereby the operator can read whether the workpiece is acceptable. The optimal route followed by the computer in the measurement cycle is as follows:

1. and (6) recording data.

2. The data is filtered.

3. The curved edge is detected to determine the curve length.

4. If calibrated, a calibration constant is calculated.

5. An accurate correction amount is calculated.

6. The radius is calculated using 80% of the curve length.

7. The radius was subtracted from the result.

8. Neglecting length, calculating peak-to-valley.

9. And displaying the result.

All this can be done in just a few seconds in a cycle, so that every minute can be

Several workpieces are inspected. The best embodiment of the invention is used for measuring the ball race, and the workload of four workpieces per minute can be achieved.

From the above, it can be appreciated that the instrument will be in different states at different times. Preferably, the status of the instrument at any given time is indicated by a digital code on the digital display 526. And the optimal number is displayed on the indicator plate 530. An example of a suitable number is as follows:

1. a ready state. In this state, the instrument is in a standby state.

2. And measuring the state. The instrument is in this state fitted with a clamp 100, which is performing a measurement cycle according to instructions from the measurement button or from the terminal.

3. And (6) calibrating. As in figure 2, but with the calibration jig in place in the apparatus.

4. And (7) printing. This is illustrative in itself.

5. The terminal is used. This is illustrative in itself.

6. And (4) error. The particular errors that have occurred are best shown by additional numbers, such as:

001 not calibrated.

002 uses a manual switch 628.

003 of an obstacle.

004 range.

005 undetected curve edges.

006 the printer is not ready.

The provision of such status codes to be noted at the top of the machine near the digital display increases the efficiency and applicability of the machine to relatively unskilled operators when using the instrument.

Figure 20 illustrates a modification of the clamp which can be adjusted to grip different sizes of ball races. In fig. 20, the assembly 110 is adjustable in the direction of arrow 700 by loosening a knob 702, the knob 702 having a bolt (not shown) passing through a slot 704 in the assembly 110. Furthermore, lever 114 is mounted on block 706, and block 706 is slidable in the direction of arrow 708 and is clamped in a selected position by means (not shown). Thus, by virtue of the positions of the adjustment plate 110 and the block 706, it is possible to grip ball races of different sizes and to correctly position the ball races in positions corresponding to the circular path followed by the stylus 22 during a measurement cycle.

Many variations are possible within the scope of the invention. For example, if the instrument is used with only one specific type of workpiece, the configuration of the apparatus may be such that the stylus follows only a single predetermined path, without the need for a replaceable fixture. Although it is preferred that the probe is retracted to a position below the fixture or support on which the workpiece is mounted, it is alternatively possible to arrange the sensor and its associated mechanism and protective housing to be to one side of the mounting position for workpiece testing, in which case the extension or retraction movement of the stylus is in a horizontal direction rather than in a straightened direction. As yet another alternative, the mechanism and protective housing may be mounted above the workpiece location. However, it is believed that the mounting shown in the drawings, in which the workpiece is positioned above the protective housing and the workpiece surface extends beyond the protective housing during testing, provides great convenience and efficiency in removing the workpiece from the instrument after it has been positioned and tested on the instrument.

It will be appreciated that the wheel arrangement shown, in which a plurality of cams are mounted on a single shaft driven by a single motor, provides an advantageous mechanism for effecting the primary motion of the stylus in a manner which provides a robust and very low cost instrument. The plurality of cams provide synchronized timing of the various movements, and since they are fixed to each other, in fact directly fixed together, the plurality of cams do not cause loss of synchronism of the movements.

The initial reception and processing of the signals from the sensors may be performed in a variety of different ways, for example by detecting the edges of the concave curved portion 4 of the workpiece, by detecting contact between the stylus and the workpiece, by detecting a particular angular position of the shaft 58, or in any other suitable manner. Because the stylus is retracted into the housing between measurements, the risk of damage to the stylus or sensor is substantially eliminated. The measurement can be done with extremely high efficiency and without interrupting the production flow, since the instrument is set up so that the sensor pair measures each of a series of identical workpieces following the same path, and since the sensor is adapted to the measurement at a relatively low speed when it is moved at high speed in extension and retraction into contact with the workpiece surface. Furthermore, when the apparatus is used with a plurality of different workpieces, the replaceable fixture provides a simple and efficient means for re-adjusting the instrument for handling such changed workpieces.

Although the instrument is described with reference to measuring radii and shapes, the instrument of the present invention can be adapted to perform other measurements, such as measuring surface structures.

Claims

1. A measuring instrument for measuring the surface of a workpiece, comprising:

· A protective case,

means for fixing the workpiece in a predetermined position with respect to said housing,

· a surface detector in the above protective housing,

drive means for moving said detector in a measurement cycle along a predetermined path, said predetermined path comprising a loop in which said detector protrudes from the housing in a first part; On the second part of the loop, the detector is measured by the surface; on the third part of the loop, the detector is retracted into the housing; the drive is adjusted so that the detector is in the second part of the path During the movement, the speed of movement is lower than the speed of movement over at least part of the path of said first or third portion.

2. An apparatus according to claim 1, wherein said drive means enables said detector to be extended at a relatively high speed and subsequently moved at a relatively low speed during said measuring operation.

3. An apparatus according to claim 1, wherein said drive means is capable of moving said detector at a relatively low speed during a measuring operation relative to the workpiece and then retracting it at a relatively high speed into said housing.

4. An apparatus according to claim 1, characterized in that the drive means is capable of causing said detector to be extended from said housing at a high speed, then moved at a relatively low speed to perform a measurement operation, and then retracted into said protective housing at a high speed middle.

5. An apparatus according to claim 3 or 4, characterized in that said detector is moved in a direction away from the position of the workpiece surface before said high speed retraction movement commences.

6. An apparatus according to claim 5, including means for adjusting the position of the detector away from the surface of the workpiece after the measuring operation has been completed.

7. An apparatus according to claim 6, including a moveable fixture for supporting the workpiece, which fixture is adapted to effect said adjustment when assembled with the apparatus.

8. An apparatus according to any one of the preceding claims, wherein said drive means is capable of moving said detector along a circular path, the detector being at a distance from the workpiece to be measured before and during extension. The surface position moves in a circular path in one direction; after the detector is stretched out, it moves toward the surface position of the workpiece to be measured.

9. An apparatus according to any one of the preceding claims, characterized in that the working support means is located on top of the protective casing.

10. An apparatus according to any one of the preceding claims, wherein said drive means comprises:

first and second cams rotatable about a common axis and fixed relative to each other,

A separate motor that drives the above cam,

• Means for coupling said cam to said detector.

11. An apparatus according to any one of the preceding claims, comprising a shutter for opening and closing an aperture in the housing through which said detector protrudes and retracts, between which said detector retracts. means for moving said shutter to a closed position when the detector is inserted into the housing and to an open position when the detector is to be extended from the housing.

12. A device according to claims 10 and 11, characterized in that said shutter is operable by another cam coaxial with the preceding first and second cams and fixed relative to said two cams, driven by said single motor cam.

13. An apparatus according to any one of the preceding claims, wherein said detector is a stylus adapted to contact the working surface.

14. An instrument according to any one of the preceding claims, which can be calibrated in conjunction with a fixture which can be attached to or removed from the instrument and which has a calibration element detected by the detector; the instrument also includes A means for sensing said calibration jig to provide a signal to initiate a calibration operation.

15. An apparatus according to any one of the preceding claims, including obstacle detection means which enable the detector to be retracted into the protective housing in time when it collides with an obstacle during the extending movement.

16. An apparatus according to claim 15, wherein said obstacle detection means is capable of detecting movement of said detector in a direction away from the surface of the workpiece.

17. A measuring instrument, comprising:

· A protective case,

· A surface detector,

the driving means for protruding the above-mentioned detector from the above-mentioned housing for measuring operations and subsequently retracting it into the housing,

- Work support means detachably fixed to the above housing, capable of holding a work of predetermined size and shape at a position on which a measurement operation can be performed with the above detector.

18. An apparatus according to claim 17, comprising a plurality of said workpiece support means adapted to have different sizes and/or shapes, the means being interchangeable.

19. An apparatus according to claim 17 or 18, including an adjustable said workpiece receiving member for workpieces of different sizes and/or shapes.

20. A measuring instrument, comprising:

· A protective case,

· A surface detector,

drive means for protruding said detector out of said housing for measuring operations and subsequently retracting it into said housing,

· a workpiece supporting device, which is fixed to the above-mentioned housing, capable of holding a workpiece having a predetermined size and shape at a position on which the measuring operation can be performed by the above-mentioned detector, and the above-mentioned workpiece supporting device is adjusted to accommodate a workpiece having a predetermined size and shape; Workpieces of different sizes and/or shapes, such that the surfaces to be measured of these workpieces can all be located at substantially the same above-mentioned position.

21. A measuring instrument, comprising:

· A housing,

means for fixing a workpiece in a predetermined position relative to said housing,

· A surface detector,

a measuring cycle control device which executes a predetermined cycle of measuring operations in which said surface detector passes over the workpiece surface fixed at said predetermined position during the measuring cycle,

• A manually controllable element which, when activated, initiates the above-mentioned cycle of measuring operations, which can be repeatedly actuated to repeat the above-mentioned cycle of operation.

22. A measuring instrument, comprising:

The device supporting the workpiece to be measured,

a detector for detecting the characteristics of the workpiece to be measured,

computerized means for carrying out measuring operations on said workpieces using said detectors,

a terminal device for inputting data into the above-mentioned computer device,

·The control device is independent from the above-mentioned terminal device, starting the control device can instruct the computer to perform the above-mentioned measurement operation once.

23. An apparatus according to claim 21, wherein said computer means is also adapted to receive an instruction from said terminal means to perform said measuring operation.

24. An apparatus according to claim 21 or 22, wherein said terminal means is detachable and separable from said apparatus.

25. An apparatus according to claim 21, 22 or 23, characterized in that said computer means are programmed to use said terminal means to carry out a programming operation which determines the measurement operation cycle and subsequently activates said independent control means The above-mentioned measurement operation process can be repeated.

26. A method of mass producing the same product, comprising:

· Produce products using mass production methods,

Presetting a measuring instrument at a condition suitable for carrying out a series of identical measuring operations on the surface of said product,

• Perform said metering operations at least on most of the above-mentioned finished products with the above-mentioned pre-set instruments.

27. A method according to claim 26, characterized in that said metrology operation is carried out in a workshop where said workpiece is manufactured.

28. A method according to claim 27, characterized in that said instrument case is capable of recording data from said workpiece and processing said data to give metrological information, said instrument is also capable of outputting said metrological information, said recording , processing and output are all carried out in the above-mentioned workshop.

29. A measuring instrument, comprising:

· A protective case,

· A sensor housed in the above housing, comprising:

· A stylus,

the driving device for driving the above-mentioned sensor, so that the above-mentioned stylus protrudes from the above-mentioned housing for measurement operation, and then retracts the stylus into the above-mentioned housing,

• Means for responding to obstacles encountered during the extension of said stylus which cause immediate retraction of said stylus into said housing.

30. An apparatus according to claim 29, wherein said stylus has a chamfered tip to deflect upon encountering an obstacle.

31. A measuring instrument, comprising:

· A housing,

· the first compartment in the above enclosure,

Electronic devices installed in the above-mentioned first compartment that generate heat during operation,

· the second compartment in the above enclosure,

· Measuring instruments sensitive to temperature changes contained in the above-mentioned second compartment,

Means for drawing ambient air into said second compartment, causing said air to flow over said apparatus and subsequently out of said second compartment, for at least limiting temperature changes of said apparatus caused by heat from said first compartment .